An ultrasonic diagnostic apparatus is a device that applies a voltage to a transducer mainly formed of a piezoelectric material, transmits ultrasonic waves generated by the transducer to a subject, and extracts various kinds of information from the reflection waves to thereby obtain internal information of the subject.
In the related art, a number of transmission circuits that apply a voltage to transducers are formed in a device main body, and the number corresponds to the number of phasing bores which is generally several tens of channels. If the number of transducers in a probe is greater than the number of phasing bores, one channel of the transmission circuits and a plurality of transducers are used by being switched by a switch that is provided in the device.
Moreover, in recent years, a 2-dimensional array ultrasonic probe in which transducers are arranged 2-dimensionally has been developed. If the transducers are arranged in a 32-by-32 arrangement, the total number of transducers becomes 1024. Thus, when all transducers are driven, a matrix-type switch or the like which requires complex control needs to be provided between the driving transducers and the transmission circuits of several tens of channels provided in the device main body.
However, such a configuration is not practical because the input capacitance or the like of the switch causes a problem. Thus, it is necessary to take measures such as limiting the transducers driven by the respective transmission circuits to a certain number of effective transducers. In all cases, it is necessary to control the matrix-type switch which requires complex control.
As described above, in the related art, in order to drive many transducers, it is necessary to transmit a number of analog transmission signals, which correspond to the number of transmission circuits and which have sufficient amplitude necessary for obtaining a diagnostic image, from an ultrasonic diagnostic apparatus main body to the probe through a cable.
Patent Literature 1 discloses an invention relating to a transmission circuit which can be incorporated into a probe.
In the transmission circuit disclosed in Patent Literature 1, the transmission circuit is configured as a switch to decrease the size thereof so as to be incorporated into a probe. By doing so, it may be not necessary to transmit an analog signal having large amplitude from the ultrasonic diagnostic apparatus main body.
However, a number of signal lines for transmitting transmission input signals corresponding to the number of transmission circuits need to be included in the cable.
Moreover, it is still necessary to use a changeover switch in order to absorb the difference in number between the transmission circuits and the transducers.
Furthermore, Patent Literature 1 does not have any description a method of controlling the internal transmission circuits from the side of the main body of the ultrasonic diagnostic apparatus, the relation of the numbers of transmission circuits and transducers, and transmission phasing.
In addition, Patent Literature 2 discloses an invention relating to control of delay in transmission phasing. Specifically, Patent Literature 2 discloses transmission means having means for controlling the transmission timing of an ultrasonic wave signal with a precision that is ¼ of a sampling clock cycle used for actual transmission by using 4-phase clock signals which are delayed in time with respect to a principal clock.
However, the proposal cannot realize a delay corresponding to finer precision since the delay precision is fixed to ¼ of the sampling clock cycle.